to offer to do something that you do not have to do, often without having been asked to do it and/or without expecting payment
Many people volunteered to help the adults learn to read.
Many individuals volunteer their time to assist in community clean-up events.
Nonprofit organizations rely on dedicated volunteers to fulfill their missions.
Students often volunteer to gain practical experience in their chosen field.
Volunteers contribute to the well-being of society through acts of kindness and service.